The present invention relates to a resist processing method for coating a resist on a substrate such as a semiconductor wafer and an LCD substrate, and developing the coated resist, and also relates to a resist processing system.
In the photolithographic process of a semiconductor device and a liquid crystal display device, a desired circuit pattern is formed by coating a resist on a semiconductor wafer and a substrate for a liquid crystal display (LCD), exposing the coated resist to light, and developing the exposed resist with a developing solution. In the developing process, a carrier gas (pressurized N.sub.2 gas) is first introduced into a tank containing the developing solution. The developing solution is sent out from the tank by the gas pressure by way of a supply line to a nozzle. Finally, the developing solution is expelled from the nozzle onto the substrate.
In such a developing process, the developing solution must be uniformly supplied over the entire substrate surface in a short time to prevent non-uniform development. If the developing solution is supplied quickly from the tank to the nozzle by increasing the pressure of the carrier gas, a large quantity of the carrier gas dissolves in the developing solution, or ambient air gets involved into the developing solution which is supplied from the nozzle. As a result, air bubbles are readily formed in the developing solution supplied to the substrate. The air bubbles attach to a substrate surface, preventing the exposure of the coated resist to the developing solution. This is a cause of the defect, "undeveloped portion of a resist". To avoid this, a deaeration apparatus has been used to separate and remove a gaseous component from the developing solution before the solution is supplied to the substrate.
However, conventional methods for removing the gaseous component from the developing solution have problems. First, a liquid component acting as an active ingredient of the developing solution is removed together with the gaseous component. The amount of this liquid component cannot be negligible. As a result, the concentration of the developing solution changes, varying the quality of the developing process. Second, in the case of the developing-solution deaeration apparatuses conventionally used, when a vacuum evacuation line of the deaeration mechanism is contaminated with the liquid component (an active ingredient in the developing solution), the evacuation capacity of the deaeration mechanism decreases, lowering the evacuation rate. Furthermore, the vacuum evacuation line itself becomes contaminated with the liquid component.